Tyrosinemia type II is an autosomal recessive condition with onset between ages 2 and 4 years, when painful circumscribed

callus A callus is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, but they may o ...

es develop on the

pressure point derive from the supposed meridian points in Traditional Chinese Medicine, Indian Ayurveda and Siddha medicine, and martial arts. They refer to areas on the human body that may produce significant pain or other effects when manipulated in a specif ...

s of the palm of the hand and

sole of the foot The sole is the bottom of the foot. In humans the sole of the foot is anatomically referred to as the plantar aspect. Structure The glabrous skin on the sole of the foot lacks the hair and pigmentation found elsewhere on the body, and it has ...

Pathophysiology

Type II tyrosinemia is caused by a deficiency of the enzyme

tyrosine aminotransferase Tyrosine aminotransferase (or tyrosine transaminase) is an enzyme present in the liver and catalyzes the conversion of tyrosine to 4-hydroxyphenylpyruvate. L-tyrosine + 2-oxoglutarate \rightleftharpoons 4-hydroxyphenylpyruvate + L-glutam ...

(), encoded by the gene ''TAT''. Tyrosine aminotransferase is the first in a series of five

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

s that converts tyrosine to smaller molecules, which are excreted by the

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...

s or used in reactions that produce energy. This form of the disorder can affect the eyes,

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different de ...

, and mental development. Symptoms often begin in early childhood and include excessive

tearing Tearing is the act of breaking apart a material by force, without the aid of a cutting tool. A tear in a piece of paper, fabric, or some other similar object may be the result of the intentional effort with one's bare hands, or be accidental. U ...

, abnormal sensitivity to light (

photophobia Photophobia is a medical symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of ...

), eye pain and redness, and painful

skin lesions A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of this s ...

on the palms and soles. About half of individuals with type II tyrosinemia are also mentally disabled. Type II tyrosinemia occurs in fewer than 1 in 250,000 individuals. Inborn errors of metabolism of phenylalanine and tyrosine

Inborn errors of metabolism of phenylalanine and tyrosine

Diagnosis

Diagnosis is made based on elevated plasma tyrosine level with skin or eye lesions.

Treatment

Dietary restrictions of phenylalanine and tyrosine.

References

External links

Amino acid metabolism disorders Autosomal recessive disorders Palmoplantar keratodermas {{Cutaneous-condition-stub

Pathophysiology

Diagnosis

Treatment

See also

References

External links